<!DOCTYPE html>
<html>
<head>
	<title>!important讲解</title>
	<style type="text/css">
		#a{
			color: green !important;
		}
		div{
			color: purple !important;
		}
	</style>
</head>
<body>
	<div class="a" id="a">a</div>
</body>
</html>